Blue Velvet Cake — red velvet's vivid blue cousin

i. Origin & history

To understand blue velvet you have to start with red velvet. 'Velvet' cakes appear in American cookbooks from the late nineteenth century, describing cakes with a particularly fine, soft crumb, often achieved with cocoa, buttermilk and a gentle acid. Red velvet took on its colour in the twentieth century; the bright red cake became strongly associated with the American South and with New York's Waldorf-Astoria, around which a well-known (and probably apocryphal) story of a guest buying the recipe grew. Food-colouring companies, notably the Texas firm Adams Extract, promoted red velvet with printed recipe cards in the mid-century, which helped fix its vivid red.

Red velvet had a large revival from the late 1980s — the armadillo-shaped red velvet groom's cake in the film Steel Magnolias, set in Louisiana, is often credited with bringing it back to national attention — and by the 2000s it was everywhere, from cupcake bakeries to wedding cakes. Once the formula was this popular, bakers began making it in other colours.

Blue velvet is one of those offshoots, alongside purple, green, pink and black velvet. There is no known inventor and no single place of origin; it emerged in American home baking and bakeries in the 2000s and spread widely online in the 2010s, especially for baby-boy showers, gender reveals, Hanukkah tables, sports-team parties and 'something blue' wedding cakes. It is not a traditional Louisiana or Southern cake in its own right, though it borrows red velvet's Southern pedigree.

In practice the cake is red velvet in all but colour: the same tender, faintly chocolatey, slightly tangy crumb, and the same cream cheese frosting. Some recipes reduce or remove the cocoa to keep the blue cleaner, which moves it closer to a buttermilk white cake.

ii. Getting a true blue rather than teal

Blue is the hardest of the velvet colours to get right, because almost everything else in the batter fights it. Cocoa powder is brown, egg yolks and butter are yellow, and blue mixed with yellow or brown turns green, teal or a murky slate. A red velvet recipe dyed blue without adjustment often bakes up an unappetising greyish green.

Three changes solve it. First, use only a little cocoa — about a tablespoon, enough for a hint of chocolate flavour and the characteristic velvet taste, but not enough to darken the batter. Second, use oil rather than butter in the cake, which also gives the soft, moist crumb red velvet is known for. Third, use a concentrated gel colour and add a tiny touch of violet or purple, which cancels the yellow and pushes the shade towards royal blue. Liquid supermarket colourings are too weak; you would need so much that the batter becomes thin and the cake tastes bitter.

The velvet texture comes from acid. Buttermilk and vinegar react with bicarbonate of soda, producing carbon dioxide for rise and a fine, even crumb; the acid also tenderises gluten, which is what gives velvet cakes their soft, close, almost plush texture. The batter is mixed only until combined — over-mixing develops gluten and gives tunnels and a tough crumb.

Finally, bake gently and do not over-bake. Blue batters brown at the edges like any cake, and browned edges look dull green against the blue interior. A moderate oven and a careful eye — pull the layers when a skewer comes out with a few moist crumbs — keep the colour bright. Trimming the domed tops and thin outer crust before assembly gives clean blue layers.

iii. Ingredients

Makes 12 servings · scroll the side panel to adjust

• 300 g plain flour
• 1 tbsp unsweetened cocoa powder
• 1 tsp bicarbonate of soda
• ½ tsp fine salt
• 300 g caster sugar
• 240 ml buttermilk, at room temperature
• 240 ml sunflower or rapeseed oil
• 2 large eggs, at room temperature
• 2 tsp vanilla extract
• 1 tsp white vinegar
• 2 tsp royal-blue gel food colour
• ¼ tsp violet gel food colour
• 450 g full-fat cream cheese, cold
• 170 g unsalted butter, softened
• 500 g icing sugar, sifted
• 1 tsp vanilla extract, for the frosting

Gel colour is essential for a strong blue without thinning the batter; check the label for 'royal blue' or 'sky blue' and use the violet sparingly. If you have no buttermilk, stir 1 tbsp lemon juice into 240 ml whole milk and leave it for 10 minutes. Use natural (non-alkalised) cocoa if you can — it is lighter in colour and its acidity helps the bicarbonate. For the frosting, choose block-style full-fat cream cheese and use it cold; spreadable tub cheese contains more water and makes a runny frosting. For a natural colour, butterfly-pea flower powder gives a soft blue, though it shifts towards purple with acid and fades in the oven.

iv. Method

1. Heat the oven to 175 °C (350 °F), or 160 °C fan. Grease two 22 cm round tins and line the bases with baking paper.
2. Whisk the flour, cocoa, bicarbonate of soda, salt and sugar together in a large bowl.
3. In a jug, whisk the buttermilk, oil, eggs, vanilla, vinegar and both gel colours until evenly blue. The batter will bake a shade darker, so aim a little lighter than the colour you want.
4. Pour the wet ingredients into the dry and whisk just until smooth and no flour streaks remain, about 30 seconds. Divide evenly between the tins.
5. Bake for 25–30 minutes, until the tops spring back when pressed and a skewer comes out with a few moist crumbs. Cool in the tins for 10 minutes, then turn out onto a rack and cool completely, at least 1 hour.
6. For the frosting, beat the butter until pale and creamy, about 2 minutes. Add the cold cream cheese and beat briefly until just smooth, then beat in the icing sugar and vanilla on low speed until thick and spreadable. Do not overbeat, or it will turn runny.
7. Level the cake tops with a serrated knife, saving the trimmings. Place one layer on a plate, spread with a thick layer of frosting, top with the second layer, and cover the top and sides with a thin crumb coat. Chill for 20 minutes.
8. Finish with the remaining frosting. Crumble the reserved blue trimmings and press them around the base or over the top, in the classic velvet-cake style. Chill for 30 minutes before slicing.

v. Tips & common mistakes

• Add a touch of violet. A pinhead of purple counteracts the yellow of the eggs and oil and stops the cake turning green or teal.
• Keep the cocoa low. A full red-velvet quantity of cocoa muddies blue into slate grey; one tablespoon gives flavour without dulling the colour.
• Use gel, not liquid colouring. Liquid colours are weak, thin the batter and can leave a bitter aftertaste at the quantity needed.
• Do not over-mix. Stir until just combined; extra mixing toughens the crumb and loses the soft velvet texture.
• Keep the cream cheese cold. Warm cream cheese, or long beating, turns the frosting soupy. Beat the butter first, then add the cheese briefly.
• Trim the browned edges. The brown crust looks greenish against the blue; trimming it and using the crumbs for decoration gives a cleaner finish.

vi. Variations

Blue velvet cupcakes use the same batter, baked at 175 °C for 18–20 minutes, making about 24. A red-white-and-blue cake stacks blue, white and red velvet layers for American national holidays. Ombré blue velvet divides the batter and tints it in three shades for a striped interior. Purple velvet and green velvet follow the same method with different colours; for a cocoa-free version, omit the cocoa and add 1 tbsp more flour.

For other American layer cakes, see the deep-chocolate Brooklyn blackout cake, the cinnamon-spiced Mexican chocolate cake and the classic strawberry shortcake. For a natural blue colour, the butterfly pea flower pudding shows what that flower does on its own.

vii. Serving & storage

Serve blue velvet cake at cool room temperature: take it out of the fridge 30 minutes before slicing so the frosting softens and the crumb is tender. Cut with a long knife wiped clean between slices to keep the blue and white layers sharp. It goes well with coffee, or with fresh blueberries and raspberries to echo the colour.

Because of the cream cheese frosting, store the cake covered in the fridge for up to 4 days. The unfrosted layers can be baked a day ahead and kept well wrapped at room temperature, or frozen, wrapped in cling film and foil, for up to 2 months; thaw in the wrapping before frosting. A frosted cake or individual slices can be frozen for a month, though the frosting loses a little of its smoothness.

ix. More from North American

• Blackout Cake — Brooklyn's deep-chocolate layer cake
• Marble Cake — swirled chocolate and vanilla
• Mexican Chocolate Cake — cinnamon-spiced chocolate
• Strawberry Shortcake — biscuit, berries and cream
• Golden Sponge — light everyday sponge cake
• Sugar-Free Chocolate Cake — rich cake without added sugar